Hydraulic means for stressing the springs of spring actuated electric switches



Nov. 13, 1962 N. JANSSON ET AL 3,064,093 MEANS FOR STRESSING THE SPRINGS OF SPRING ACTUATED ELECTRIC SWITCHES 2 Sheets-Sheet 1 TOR. Alf/3 J M 5' EN 7374- H'd/M B Nov. 13, 1962 N. JANSSON ETAL 3,064,093

HYDRAULIC MEANS FOR STRESSING THE SPRINGS OF SPRING ACTUATED ELECTRIC SWITCHES Filed June 15, 1960 2 Sheets-Sheet 2 Alf/s JAuss'JxM 9 Hd/m BY 0%,MQW

United States Patent Ofitice 7 3,064,093 Patented Nov. 13, 1962 3 064 093 HYDRAULIC MEAI QS FOR STRESSING THE SPRINGS OF SPRING ACTUATED ELEC- TRIC SWITCHES Nils Jansson and Tage Holm, Ludvika, Sweden, assignors to Allmanna Svenska Elektriska Aktiebolaget, Vasteras,

Sweden, a Swedish corporation Filed June 15, 1960, Ser. No. 36,191 2 Claims. (Cl. ZOO-82) This invention relates to means for stressing the actuating springs for high voltage electric switches.

In high voltage spring actuated switches, the actuating springs must be stressed after each switching-on so that the switch can be prepared for another actuation.

It is already known to use hydraulic means comprising a piston for stressing actuating springs. In the known constructions, however, the piston of the spring stressing device is rigidly secured to the actuating springs, or at least to one of them.

When the actuating springs and the piston are rigidly connected, the actuating springs, in the switching movement, must accelerate the mass of the piston and piston rod, and this is a disadvantage if a rapid switching movement is aimed at.

The present invention is characterised in that the stressing means is disconnected from the actuating means in the stressed position of the actuating means. Since the actuating springs are mechanically disconnected from the piston and piston rod of the stressing means, they do not have to accelerate the mass thereof and the switching movement of the switch is therefore more rapid.

Alternatively, the elastic force of the actuating springs may be reduced for a certain switching period.

According to a subsidiary feature of the invention the stressing means comprises a spring-loaded piston movable in a cylinder and capable of being locked in its rest position. By reason of the locking means which locks the piston of the stressing means when the actuating spring of the switch has been stressed, a plurality of switches may be coupled to a common pump aggregate. Preferably, the locking means for the piston is also so disposed that it locks the piston in stressed position as long as the hydraulic system is under excess pressure and actuates a pump aggregate connected to the hydraulic system. This means that a stressing means cannot stress the actuating means after the switching-on of its associated switch, so long as another stressing means is carrying out its stressing movement, because the piston of the stressing means is locked in stressed position as long as the hydraulic system is under excess pressure. By this locking arrangement a stressing means will always complete its stressing movement before another stressing means can begin. Without this locking arrangement, a stressing means which has started would be interrupted in its normal movement if another stressing means started and, because the output of the pump aggregate is constant, the two stressing means would carry out their stressing movements more slowly than normally.

Two embodiments of hydraulic stressing means in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic view showing a first embodiment of the stressing means in the rest position and the actuating springs stressed,

FIGURE 2 shows the stressing means of FIGURE 1 immediately after a switching-on,

FIGURE 3 shows the stressing means of FIGURE 1 during a stressing movement, and

FIGURE 4 is a schematic cross-sectional view through the cylinder and the locking means of a second embodiment of the stressing means.

In all the figures the numeral 1 designates the liquid container of a pump aggregate, and 2 designates a pump driven by an electric motor 10 supplied via a controlling switch 8. 3 is a valve member in a valve housing 4, and 7 is a pipe between the pump aggregate and the stressing means. The pump aggregate is provided with a safety valve 9 the opening pressure of which is sufliciently high to permit undisturbed functioning of the arrangement under normal conditions. The pump aggregate is also provided with a pressure switch 6 comprising an electrical contact 5. The stressing means comprises a cylinder 15 and a piston 17 movable therein, the latter being springloaded by a compression spring 16. The stressing means also comprises a pivotally mounted locking means 13 and an electrical contact means 14.

FIGURES 1 to 3 show the pivotally mounted switch arm 11, release member 18 and the actuating spring 12 of a switch associated with the stressing means. FIGURE 1 also shows how more than one stressing means may be connected to pipe 7.

FIGURE 4 shows a flange 19 on the piston 17 and a switch arm 20 of the lever rod type attached to thepiston.

Referring now to FIGURES l to 3, when the switch arms 11 in all switches are locked, the positions of the parts of the stressing means are as shown in FIGURE 1. When a switch is switched-on, the releasing member 18 of the switch releases the switch arm 11 and this moves counterclockwise under the influence of its stressed spring 12 and in its lower position influences the locking means 13. The locking means 13 moves clockwise into the position shown in FIGURE 2, in which it releases the piston 17 and closes the contact means 14 to complete a circuit through the operating coil of the control switch 8. The control switch 8 closes and becomes self-holding through its own contact d. The motor 10 is started and liquid is pumped by the pump 2 from the container 1 into the valve housing 4, which results in the valve member 3 being pressed against a seating in the bottom of the valve housing (as shown in FIGURE 2). The liquid then forces its way past a spring-loaded ball valve in the member 3 and through the pipe 7 to the stressing means. The piston 17 in the cylinder 15 is forced upwards and the spring 12 of the switch is re-stressed. During the stressing movement, which is shown in FIGURE 3, the locking means 13 returns to its rest position and the contact 14 is opened. The motor 10 is not switched 01f, however, because the coil of the control switch 8 receives current through the contact 5 of the pressure switch 6. When the switch arm 11 reaches the position corresponding to the fully-stressed actuating spring, it is locked by the releasing member 18. The piston 17 cannot continue its movement, so that the pressure in the hydraulic system rises and the pressure switch 6 is influenced to open its contact 5. This de-energises the coil of the control switch 8 so that the motor 10 is shutoff. The valve member 3 then returns to the position shown in FIGURE 1 in which the pipe 7 is in direct communication with the container 1. The piston 17 is returned to its rest position by the spring 16 and locked by the lock 13. The liquid flows back into the container 1.

The locking arrangement according to FIGURE 4 operates in the following way: when a switch is switched on and its actuating spring thereby unloaded, the switch arm 11 moves counterclockwise into the position shown in dotted lines in the figure. The switch arm 11 thereby in fluences through the spring 21, the locking means 13 which releases the piston 17 and closes the contact 14. In the same way as previously the motor 10 is started and the pump 2 delivers liquid to the stressing means. The piston 17, by reason of the liquid pressure, then moves in the cylinder 15 and influences the switch arm 11 through the arm 20 so that the actuating spring of the switch is again stressed. If a second switch is switched on during the period during which the first switch is stressed, its switch arm 11 moves counterclockwise to the position shown in dotted lines.

The spring 21 is stressed in the position shown in dotted lines but it cannot lift up the locking means 13 because this is locked by the projection 19 being pressed against the locking means 13 by the excess pressure acting on the piston. When the actuating spring of the first switch is stressed, the pump aggregate is switched off, whereupon the piston 17 and its spring 16 forces the liquid back into the container and the piston returns to its rest position. When the excess pressure no longer exists in the hydraulic system, the pressure of the piston projection 19 against the lock 13 in the second switch ceases. The spring 21, which lies in the position shown in dotted lines is then able to influence the locking means 13 so that this moves counterclockwise. The piston 17 is released and the contact 14 is closed. The pump aggregate then starts in order to stress the actuating spring of the second switch.

We claim:

1. In a mechanism having an arm operatively connected to an electric switch spring and movable between a first position in which the spring is stressed and a second position in which the stress on the spring is relieved, a cylinder having a piston movable therein between a first and a second position, said piston having means thereon operatively engageable with the arm for moving the arm from its second to its first position as the piston moves from its second to its first position, means operatively connected with the piston for resiliently urging it towards its second position, means to supply fluid under pressure to said cylinder to move the piston from the second to the first position, locking means engageable with the piston for holding it in its second position, said arm in its second position being operatively connected with said locking means to move it to releasing position, means responsive to movement of the locking means to releasing position to actuate said pressure fluid supply means, and means responsive to a rise in pressure of the pressure fluid above a predetermined value to render said pressure fluid supply means inoperative to permit the return of the piston to the second position by the resilient means.

2. In combination with a plurality of mechanisms as claimed in claim 1 having a common pressure fluid supply means, each piston and locking means having cooperating means thereon to hold the locking means in locking position when the pressure in the cylinder exceeds a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,270 Westervelt June 12, 1945 2,598,446 Schneider May 27, 1952 2,920,607 Barkan Ian. 12, 1960 FOREIGN PATENTS 142,860 Switzerland Ian. 2, 1931 

